Joint Land Attack Cruise Missile Defense Elevated Netted Sensor (JLENS)

A large unmanned U.S. military aerostat that broke loose from its tether Wednesday and floated over Pennsylvania for several hours is back on the ground after deflating. There were no reports of injuries or serious damage, but about 30,000 people lost electricity as the aerostat 's cables hung down when it drifted, snapping power lines on the ground.

On 26 January 2012, the Department of Defense announced, in a report on defense spending priorities, that the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS) had been curtailed due to concerns about program cost and operational mobility.

The Joint Land-Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS) consists of an aerostat with radars to provide over-the-horizon surveillance for defense against cruise missiles. JLENS is primarily intended to tackle the growing threat of cruise missiles to US forces deployed abroad. The system enhances cruise missile detection and engagement ranges with current air defense weapons such as PATRIOT, Navy SM-2 missile, the Advanced Medium Range Air-to-Air Missile, and ultimately the Medium Extended Air Defense System and the Corps Surface-to-Air Missile System.

JLENS is a large, unpowered elevated sensor moored to the ground by a long cable. The system consists of two 74-meter aerostats which work in tandem and can stay up for 30 days. One has a surveillance radar and the other has a fire control radar. The surveillance radar is built to pick up multiple targets. It passes data to the fire control radar which provides precision tracking information over several joint networks.

Designed to identify and track cruise missiles through a pair of aerostats tethered 10,000 feet in the air, JLENS is targeted at an attack that military planners expect in the near future. The JLENS long-range surveillance radar weighs 6,600 pounds, as much as a large sport utility vehicle. There is no weapon as part of the system, but a big part of the system is its ability to integrate with other systems. The first such system that comes to mind is a Patriot missile battery, which Raytheon also makes. Other so-called pointy end systems that could receive JLENS targeting data include SLAMRAAM/CLAWS and MEADS. Manufactured by Maryland-based TCOM, the 74-meter-long (three-quarters of a football field) aerostat is based on a commercial 71-meter aerostat already built by the company. Lift is provided by low-pressure helium gas.

From its position above the battlefield, the elevated sensors will allow incoming cruise missiles to be detected, tracked, and engaged by surface-based air defense systems even before the targets can be seen by the systems. The elevated sensors have several characteristics, which may make them especially suited to CMD. They are less expensive to buy and operate than comparable fixed-wing aircraft. This makes them the most affordable alternative for achieving a near-term CMD.

In addition to providing a significant cruise missile defense capability, the JLENS system will also be capable of tracking surface moving targets and tactical ballistic missiles during their boost phase, and passing target data to various weapon systems and platforms across the military services. The ability to perform multiple missions for extended periods of time and interoperate with other systems such as the Army PATRIOT and the Navy Standard Missile makes JLENS a true enabler of Joint Battlespace Integration. This system is going to make a big difference on the battlefield of the future.

The elevated sensors can stay aloft up to 30 days at a time providing 24-hour per day coverage over extended areas. JLENS will operate at altitudes between 10,000 and 15,000 feet; be capable of detecting long range, terrain masked targets; and provide an effective fire control solution for joint theater air and missile defense weapon systems. Additionally, it can operate from sites on both land or sea, and is tactically relocatable. Comparing these capabilities against the performance of our current sensor systems, the value added of JLENS is readily apparent.

The internal pressure of JLENS is about the same as the exterior pressure. This makes them extremely difficult to shoot down. These elevated sensors can absorb lots of punctures before they lose altitude. When they do, they come down so slowly that they can be reeled in, repaired easily, and sent right back up. In the long term, JLENS would complement fixed-wing aircraft performing a similar mission, and this will provide the U.S. more robust and flexible CMDs. Mooring systems for large JLENSs covering major portions of a theater of operations would probably be relatively permanent. For short or medium range surveillance and fire control, JLENSs would be smaller and the mooring systems could be transportable or ground-mobile.

A JLENS system consists of two aerostats, one containing a Surveillance Radar (SuR) and one containing a Precision Track Illumination Radar (PTIR). The aerostats are non-developmental, 71-meter, unmanned, tethered, non-rigid aerodynamic structures filled with helium and air. JLENS uses a 71-meter aerostat platform for the cruise-missile-defense radars being developed. The aerostat can reach heights up to 15,000 feet above ground level with a 4,000-pound payload. Part of the JLENS development effort is focused on enhancing the system's mobility and transportability. JLENS also owns a smaller-size aerostat system. This system is an excellent candidate for dedicated communications missions. The aerostat can raise a 150-pound payload to 1,000 feet AGL. Operating characteristics of aerostats depend on base altitude and temperature. For example, on a cool day stationed at sea level, the aerostat will fly higher than on a warm day stationed at 4,000 mean sea level.

Each aerostat is tethered to a mobile mooring station and attached to a processing station via a fiber optic/power tether. The SuR provides the initial target detection and then cueing to the PTIR, which generates a fire control quality track. The JLENS system is integrated into the Joint Tactical Architecture via Link 16, Cooperative Engagement Capability, Single-Channel Ground and Air Radio System, and Enhanced Position Location Reporting System. The system provides key contributions to generation of a Single Integrated Air Picture, through the fusion of high accuracy long-range tracking and target classification information with that of other sensors in the Joint Air and Missile Defense architecture. Both radar systems will include Identification, Friend or Foe interrogators.